package ext.opensource.netty.common.utils;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;

public class IdWorker {

	/**
	 * 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
	 */
	private final static long TWEPOCH = 1288834974657L;
	/**
	 * 机器标识位数
	 */
	private final static long WORKER_ID_BITS = 5L;
	/**
	 * 数据中心标识位数
	 */
	private final static long DATA_CENTER_ID_BITS = 5L;
	/**
	 * 机器ID最大值
	 */
	private final static long MAX_WORKER_ID = -1L ^ (-1L << IdWorker.WORKER_ID_BITS);
	/**
	 * 数据中心ID最大值
	 */
	private final static long MAX_DATA_CENTER_ID = -1L ^ (-1L << IdWorker.DATA_CENTER_ID_BITS);
	/**
	 * 毫秒内自增位
	 */
	private final static long SEQUENCE_BITS = 12L;
	/**
	 * 机器ID偏左移12位
	 */
	private final static long WORKER_ID_SHIFT = IdWorker.SEQUENCE_BITS;
	/**
	 * 数据中心ID左移17位
	 */
	private final static long DATA_CENTER_ID_SHIFT = IdWorker.SEQUENCE_BITS + IdWorker.WORKER_ID_BITS;
	/**
	 * 时间毫秒左移22位
	 */
	private final static long TIMESTAMP_LEFT_SHIFT = IdWorker.SEQUENCE_BITS + IdWorker.WORKER_ID_BITS
			+ IdWorker.DATA_CENTER_ID_BITS;

	/**
	 * 
	 */
	private final static long SEQUENCE_MASK = -1L ^ (-1L << IdWorker.SEQUENCE_BITS);
	/**
	 * 上次生产id时间戳
	 */
	private static long lastTimestamp = -1L;
	/**
	 * 0，并发控制
	 */
	private long sequence = 0L;

	private final long workerId;
	/**
	 * 数据标识id部分
	 */
	private final long datacenterId;

	public IdWorker() {
		this.datacenterId = IdWorker.getDatacenterId(IdWorker.MAX_DATA_CENTER_ID);
		this.workerId = IdWorker.getMaxWorkerId(datacenterId, IdWorker.MAX_WORKER_ID);
	}

	/**
	 * @param workerId
	 *            工作机器ID
	 * @param datacenterId
	 *            序列号
	 */
	public IdWorker(final long workerId, final long datacenterId) {
		if (workerId > IdWorker.MAX_WORKER_ID || workerId < 0) {
			throw new IllegalArgumentException(
					String.format("worker Id can't be greater than %d or less than 0", IdWorker.MAX_WORKER_ID));
		}
		if (datacenterId > IdWorker.MAX_DATA_CENTER_ID || datacenterId < 0) {
			throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0",
					IdWorker.MAX_DATA_CENTER_ID));
		}
		this.workerId = workerId;
		this.datacenterId = datacenterId;
	}

	/**
	 * 获取下一个ID
	 *
	 * @return
	 */
	public synchronized long nextId() {
		long timestamp = timeGen();
		if (timestamp < IdWorker.lastTimestamp) {
			throw new RuntimeException(
					String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds",
							IdWorker.lastTimestamp - timestamp));
		}

		if (IdWorker.lastTimestamp == timestamp) {
			// 当前毫秒内，则+1
			sequence = (sequence + 1) & IdWorker.SEQUENCE_MASK;
			if (sequence == 0) {
				// 当前毫秒内计数满了，则等待下一秒
				timestamp = tilNextMillis(IdWorker.lastTimestamp);
			}
		} else {
			sequence = 0L;
		}
		IdWorker.lastTimestamp = timestamp;
		// ID偏移组合生成最终的ID，并返回ID
		final long nextId = ((timestamp - IdWorker.TWEPOCH) << IdWorker.TIMESTAMP_LEFT_SHIFT)
				| (datacenterId << IdWorker.DATA_CENTER_ID_SHIFT) | (workerId << IdWorker.WORKER_ID_SHIFT) | sequence;

		return nextId;
	}

	private long tilNextMillis(final long lastTimestamp) {
		long timestamp = this.timeGen();
		while (timestamp <= lastTimestamp) {
			timestamp = this.timeGen();
		}
		return timestamp;
	}

	private long timeGen() {
		return System.currentTimeMillis();
	}

	/**
	 * <p>
	 * 获取 maxWorkerId
	 * </p>
	 */
	protected static long getMaxWorkerId(final long datacenterId, final long maxWorkerId) {
		final StringBuffer mpid = new StringBuffer();
		mpid.append(datacenterId);
		final String name = ManagementFactory.getRuntimeMXBean().getName();
		if (!name.isEmpty()) {
			/*
			 * GET jvmPid
			 */
			mpid.append(name.split("@")[0]);
		}
		/*
		 * MAC + PID 的 hashcode 获取16个低位
		 */
		return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
	}

	/**
	 * <p>
	 * 数据标识id部分
	 * </p>
	 */
	protected static long getDatacenterId(final long maxDatacenterId) {
		long id = 0L;
		try {
			final InetAddress ip = InetAddress.getLocalHost();
			final NetworkInterface network = NetworkInterface.getByInetAddress(ip);
			if (network == null) {
				id = 1L;
			} else {
				final byte[] mac = network.getHardwareAddress();
				id = ((0x000000FF & (long) mac[mac.length - 1])
						| (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
				id = id % (maxDatacenterId + 1);
			}
		} catch (final Exception e) {
			System.out.println(" getDatacenterId: " + e.getMessage());
		}
		return id;
	}

}
